Fractional distillation column



July 27, 1954 LUPFER 2,684,936

FRACTIONAL DISTILLATION COLUMN Filed Nov. 8, 1949 INVENTOR. GEORGE L. LUPFER BY 0% @II/MM ATTOEIV'EYS.

Patented July 27, 1954 FRACTIONAL DISTILLATION COLUMN George L. Lupfer, Bedford, Ohio, assigncr to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio Application November 8, 1949, Serial No. 126,150

4 Claims. I

For high efficiency fractional distillation, the bubble cap type of tower is in wide usage. It has however, certain well known disadvantages. The necessity of the vapor to change direction of flow and encounter resistance in bubbling down under the caps and out through the liquid occasions an undesirable pressure difierential, so that, for instance, in high vacuum distillation there is quite a material pressure drop through the tower. Attempts have been made to fractionate by a shower type contact, with a tower containing trays with perforated bottoms instead of bubble caps, and each tray filling only a portion of the crosssectional area. The rising vapors, flowing essentially perpendicularly and against the liquid shower tend to throw the liquid droplets against the tower wall and cause creeping upward, and interfere with the desired fractionation. The overall efficiency of such a shower device is lower than that of the bubble cap tower. In accordance with the present invention, it now becomes possible to fractionate with remarkably high efficiency, and at the same time obviate the serious pressure drop which characterizes the bubble cap type of tower. And, as compared with the here tofore known shower type, the effective area is raised from that of a conventional shower type tower in which the effective area is only a minor per cent of the total, to an effective area almost equal to the total cross sectional tower area. Other objects and advantages of the invention will appear from the following description.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a side view, partly broken away, illustrating tower construction in accordance with the invention; and

Fig. 2 is a transverse sectional view.

In general, tower shell structure 2 may be along the lines usual with bubble cap towers, that is, a vertical cylindrical shell. And, the top reflux stream also may be directed into the tower at the top, however, in the present invention the reflux inlet 3 is particularly well distributed across the sectional area. In the center of the tower is a support 4, which for instance may be in tubular form, closed off at the top and bottom. Its

center position and size prevents channeling of vapors and compels flow as determined by the trays. Trays are carried between the center support 4 and the outside shell 2. A pecularity here however is that the trays are placed in a spiralstair series. In gross relation, the arrangement is like that of a spiral stairway, as for instance in a lighthouse. A further pecularity of the tray system in the present invention is that each tray has its floor perforated with holes of a diameter to feed liquid from the tray as a shower of falling droplets thereunder. Depending upon the material fractionated, the perforations may be gauged to proper droplet formation. For example, to inch holes would be suitable for some materials. Each tray 5 is provided with a weir 6 on the down stream side, to maintain the desired head of liquid on the perforated droplet-forming floor without overflowing. A pecularity of the structure is that from the overflow Weir there extends downward in each case a vertical partition I to seal off the opening between a tray and the one below it. In effect, the vapor passway between stair-like steps is closed by a riser, i. e. partition i, thus compelling the vapor stream rising from below to take a spiral course, flowing around and upwardly between trays. Each tray may range from a sector of a few degrees to 180, but preferably about Thus, liquid passing down from the top of the tower proceeds spiral-wise through a series of bodies of liquid on the trays, and is showered in rain-like form successively. The droplets would fall vertically if there were no rising vapor stream. At the same time, the vapor stream rises spirally passing up the staircase of trays, and under each in succession being compelled to proceed through the downpour of liquid shower. As can be seen, the impact of the vapor, being generally transverse to the direction of downflow of the liquid, does not tend to hold up liquid and interfere with fractionation as is the case where vapor flow is directed upward against downflow of liquid droplets. Moreover, the spiral arrangement in the present invention occasions an element of centrifugal action which assists in disengaging liquid from the rising vapor stream; and liquid entrainment up the tower, which has been a problem with fractionating equipment of heretofore known types, is greatly reduced. In some cases, it is advantageous to position vanes or vertical bafiles N at spaced points around the interior wall of the tower shell to assist in disengaging and draining the liquid from the tower walls.

The operation of fractionating in accordance with the invention is readily understood from the foregoing. The feed stock may be heated either inside or outside the tower by conventional means. A rising stream of vapor from the feed passes spiral-wise around and around and upwardly through the space between trays, and at the same time liquid reflux coming down from above is showered "inheavy downfall through the traveling vapor stream. One or more side streams of fractionated liquid may be taken off from points of the tower where desired. The tray where such a side stream is-takenbff, may omit the perforations in its floor, and the weir will of course be high enough that the liquid level covers the draw-off outlet. -Thus, if liquid be withdrawn from a 90 sector, it will amount to approximately 25% of thedowncoming liquid; and if it is desired to withdraw a greater amount of liquid the perforations in the next sector above may be omitted, so that the liquid will then overflow to the sector below and be withdrawn at the aforementioned outlet. The tower bottoms can bedrawnoif below, as in known practice.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In fractional distillation apparatus,.a tower shell, a central axial'support therein, a spiralstair series of horizontal trays between said shell and said support, said spiral-stair series of trays constituting'more than one-revolution and said trays each constituting a liquid-containing .sector but leaving a much larger sector vapor passway, and a vertical partition extending. upwardly from one edge of each tray-to a level slightly trays-each constituting a liquid-containing sector but leaving a much larger sector 'va'por'pass- ,way,'a vertical partition extending upwardly from one edge of each'tray toa-level slightly above 4 the adjacent edge of the next higher tray in the series of trays so that said partition forms an overflow weir with said last-mentioned tray, said trays having perforated floors, and means below the series of trays providing generation of vapors from liquid.

3. In fractional distillation apparatus, a tower shell, a central axial support'therein, a spiralstair series of horizontal trays between-said shell and said support, said spiral-stair series of trays constituting more than one revolution and said trays each constituting a liquid-containing sector but leaving a much larger sector vapor passway, and a, vertical partition extending upwardly from one edge of eachtray to a level slightly above the a'djacente'dge of the next higher tray in the seriesof trays so that said partition forms an overflow weir with said last-mentioned tray, a side'stream outlet from at least one tray for liquid draw-01f, said l-trays having perforated floors except that tray which is directly above said liquid draw-off.

4. In fractional distillation apparatus, -atower shell, a central axial'support therein, aspiralstair-series of horizontal trays between said shell and saidsupport, said spiral-stair series of trays constituting more than one revolution .and said References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,138,460 Derby May 4,1915 1,163,437 Morison Dec. 7, 1915 1,240,368 Reese Sept. 18,1917 1,262,522 Lambert Apr. 9, 1918 1,804,554 Dubbs May '12, 1931 1,937,958 Huff Dec. 5, 1933 1,950,313 'Linde Mar. '6, 1934 2,310,829 Becker Feb. 9, 1943 2,317,101 Lecky Apr. 20, 1943 2,581,051 Smith Jan. 1, 1952 FOREIGN PATENTS Number Country Date 299,075 Great Britain Oct. 22, 1928 840,086 France Apr. '18, 1939 

1. IN FRACTIONAL DISTILLATION APPARATUS, A TOWER SHELL, A CENTRAL AXIAL SUPPORT THEREIN, A SPIRALSTAIR SERIES OF HORIZONTAL TRAYS BETWEEN SAID SHELL AND SAID SUPPORT, SAID SPIRAL-STAIR SERIES OF TRAYS CONSTITUTING MORE THAN ONE REVOLUTION AND SAID TRAYS EACH CONSTITUTING A LIQUID-CONTAINING SECTOR BUT LEAVING A MUCH LARGER SECTOR VAPOR PASSWAY, AND A VERTICAL PARTITION EXTENDING UPWARDLY FROM ONE EDGE OF EACH TRAY TO A LEVEL SLIGHTLY ABOVE THE ADJACENT EDGE OF THE NEXT HIGHER TRAY IN THE SERIES OF TRAYS SO THAT SAID PARTITION FORMS SAID OVERFLOW WEIR WITH SAID LAST-MENTIONED TRAY, SAID TRAYS HAVING PERFORATED FLOORS. 